One of the fundamental properties of the human brain is its ability to adapt to changing intrinsic (e.g., growth) and extrinsic (e.g., changing environment) conditions. Adaptive sensory-motor behavior usually requires the transformation and integration of information from different modalities and different coordinate systems. For example, in visually- guided reaching, the location of an object in visual coordinates needs to be mapped to motor commands that move the arm to the visual target. This transformation, known as the visuomotor map, needs to be adapted if environmental conditions change, e.g., due to perturbations of the visual input. Recent data suggest that aging degrades visuomotor adaptation in humans. However, little is known about the mechanisms underlying age- related changes in sensory-motor processing and adaptation. In the proposed research, two major hypotheses will be systematically investigated using behavioral and computational neuroscience methods: 1) The rate of visuomotor adaptation is reduced in the elderly (reduced plasticity) and 2) Increased motor variability (e.g., reduced . signal-to- noise ratios) in aging contributes to reduced visuomotor adaptation. This theory-driven research has both theoretical and clinical relevance, as the proposed experiments will provide a detailed quantitative description of the effects of aging on visuomotor adaptation, whereas the computational model will help the understanding of these age-related changes. Overall this research will elucidate which interventions are likely to prevent or modify these changes.